Requirements on transducers for ultra-high recording densities (greater than 60 Gb/in2) place certain constraints on the properties of the read and write heads needed to achieve this. These fundamental constraints have a profound influence on the design and fabrication of the read/write transducers. To achieve extremely high recording densities, Giant Magnetoresistance (GMR) reader design has to be capable of very high linear bit density (BPI) and also very high track density (TPI). Consequently, GMR devices continue to be pushed to narrower track widths and to thinner free layers to maintain high signal output in spite of reductions in track width and reduced gap length.
A critical issue for a very narrow track width is possible large amplitude and sensor stability loss. One approach that has been proposed to alleviate the amplitude loss and sensor stability concern is to use a lead overlay design. In lead overlay design, MR sensor track width is defined by conductor lead edge while the contiguous hard bias junction is placed outside the lead overlay.
For reader device situated within a reduced gap (i.e. thin upper dielectric layer), lead overlay topography becomes very critical. The bi-layer resist structure for conductor lift-off is normally made with an undercut in the bottom resist layer. For a very narrow track width, there is no room for creating this resist undercut so conductor lead structures formed using conventional lift-off process are exposed to a high probability of ending up with bridging conductor leads as well as conductor lead fencing. The former results in current shunting, while the latter leads to sensor to shield shorts. Additionally, lead overlays formed during a conductor lead lift-off process is usually associated with poor contact resistance at the lead overlay and GMR interface.
In the present invention the bias and conductor lead substructures are formed without the use of a liftoff process.
A routine search of the prior art was performed with the following references of interest being found: U.S. Pat. No. 5,985,162 (Han et al.), U.S. Pat. No. 6,103,136 (Han et al.), and U.S. Pat. No. 6,007,731 (Han et al.) all show lead lift off processes. In U.S. Pat. No. 5,966,273, Matsumoto et al. show a lead process while in U.S. Pat. No. 5,491,600, Chen et al. show a multi-layered lead and associated process.